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Food and Drug Interactions You Should Watch Out For

With someone in our household who takes meds, I am always on the lookout for food-drug interactions and ways to keep us all healthy.

Grapefruit, alcohol, and chocolate can interact with prescription and OTC medications to make them weaker or stronger than intended.

Grapefruit, alcohol, and chocolate can interact with prescription and OTC medications to make them weaker or stronger than intended.

What Is a Food-Drug Interaction?

Who would believe that one of America’s favorite breakfast juices can cause serious side effects when taken with certain medications? Grapefruit juice has actually been identified as a source of sometimes serious interactions with over 50 different drugs. Or that chocolate, everyone’s favorite comfort food, can cause an increase in the effect of certain psychostimulant drugs approved for the treatment of attention-deficit hyperactivity disorder (ADHD), and can be downright dangerous if consumed with certain antidepressants?

The components that make up the foods and beverages we consume have the potential to interact with certain medications. Whenever a food or a beverage changes the intended effects of a medication in the body—whether a prescription medication or an over-the-counter (OTC) drug—the change is considered a food-drug interaction.

Grapefruit is such a known culprit that it is routinely tested with new drugs as they go through testing by the FDA.

Risk Factors

The risk of food and drug interactions is influenced by several factors, including a person's age, body composition, overall health, and whether the drug is taken before or after the food.

One of the most common ways that foods and beverages interact with medications is by changing the way drugs are metabolized in the body. Some foods can prevent medications from being absorbed altogether, as with milk and certain sub-classes of antibiotics, while others can actually cause an increase in absorption or new/magnified side effects. Depending on the specific food and drug combination, the interactions may:

  • cause the intended effects of the medication to be increased;
  • cause the intended effects of the medication to decrease;
  • cause the absorption of the medication into the body to be slowed down; or
  • cause the medication to remain in the system longer.

Any of these situations can have potentially dangerous consequences. As an example, taking Calcium Channel Blockers (regularly prescribed for high blood pressure) with grapefruit juice can cause the effects of the drug to be increased in the body. This can lead to low blood pressure, headache, dizziness, and increased heart rate in some people. And you don't have to swallow the pill with grapefruit juice for it to be a problem—the effects of eating grapefruit or drinking grapefruit juice can remain in the body for up to three days.

5 Common Foods That Can Interact With Drugs

Though there are many others, here are five common foods that can alter the effects of a drug.

  • Grapefruit juice
  • Green, leafy vegetables
  • Natural black licorice
  • Salt substitutes
  • Tyramine-containing foods

Vitamins and Supplements

Foods that are rich in certain vitamins and minerals can also cause serious interactions with some medications. As an example, foods high in potassium can cause some potentially serious side effects for some people taking ACE inhibitors which are widely used to control high blood pressure. ACE inhibitors can cause potassium levels in the blood to increase, and if a person's diet is also high in potassium-rich foods including bananas and oranges, the increased potassium levels in the blood can lead to low heart rate or abnormal heart rhythm.

Dietary and herbal supplements also have the potential to cause serious interactions. St. John's Wort, used to treat mood swings, is thought to interact negatively with many medications. The challenge lies in the fact that herbal remedies and so-called 'natural' supplements are not tested the way that other drugs are when looking for possible interactions. Always tell your doctor or pharmacist about any supplements you are taking.

ACE inhibitors don't mix with potassium-rich foods, like oranges and bananas.

ACE inhibitors don't mix with potassium-rich foods, like oranges and bananas.

Common Drug Interactions

There are many different foods and beverages that can interact negatively with medication. Some common culprits include:

Salt Substitutes

People diagnosed with high blood pressure are often put on low sodium diets to restrict salt intake and may choose to use salt substitutes containing potassium. Folks taking digoxin need to be careful with these substitutes, as excess potassium can interfere with the effectiveness of this heart drug.


We all know about the dangers of drinking alcohol when taking any medication— whether prescription or over-the-counter. Alcohol can cause side effects to become more pronounced and can also increase or decrease the effectiveness of certain drugs.

Labels on over-the-counter pain relievers based on the ingredient acetaminophen contain warnings about taking the medication with alcohol, as serious liver damage can occur if you have more than 3 alcoholic drinks every day while taking the pain reliever. The same holds true with pain relievers that have naproxen as the main ingredient. This class of drug is a non-steroidal anti-inflammatory (NSAID) that can cause stomach bleeding if a person has 3 or more alcoholic drinks every day while using the product.

Natural Black Licorice

Glycyrrhiza, used to flavor natural black licorice, can cause a dangerous imbalance in sodium and potassium in the body if too much licorice is consumed. It can lead to depletion of potassium in the body and cause the effects of drugs like digoxin to be enhanced. It can also interfere with high blood pressure medicines and with warfarin.


Grapefruit and grapefruit juice contains a compound that interferes with the way a certain enzyme in the digestive system works. This interference allows medications to pass more readily into your bloodstream, meaning higher than intended levels of the drugs. And the effects can linger; one glass of grapefruit juice can inhibit the digestive enzymes for up to three days, meaning that taking the medication within that 3-day window can have potentially serious results.

Certain blood pressure meds can cause a person’s blood pressure to go dangerously low when taken with grapefruit juice because the effects of the drug are boosted significantly by the interaction. Though clinical studies are incomplete for some drugs, the number of commonly prescribed medications that interact with grapefruit juice is estimated to be over 50, and is thought to include such popular medications as “the little blue pill”.

Green, Leafy Vegetables

We are told to eat more of these as they are so good for us, and yet they can be potentially life-threatening for certain individuals. People taking blood thinners need to be very careful about the amount of Vitamin K in their diets, as this Vitamin can actually negate the effect of the blood thinner. Green leafy vegetables are high in Vitamin K, and for some people taking Coumadin® (warfarin), as an example, eating too many green leafy veggies can potentially cause serious blood clots.


Chocolate contains caffeine, which is a common stimulant. If chocolate is eaten with certain medications, the effects can be dangerous. The caffeine in chocolate can cause the effects of stimulant medications including methylphenidate to be intensified. Chocolate can have the opposite effect on sedatives, causing their intended effects to be decreased. And the amount of chocolate required is not that great; one ounce of dark chocolate can contain up to 35 grams of caffeine, enough to potentially cause a problem.

Tyramine-Containing Foods

Chocolate also contains tyramine, an amino acid that can cause an increase in blood pressure. Certain drugs are known to interfere with the breakdown of tyramine in the body, potentially leading to dangerously high levels. If you are taking MAO inhibitors to treat depression, elevated levels of tyramine can trigger a dangerous increase in blood pressure, potentially leading to a stroke.

Drugs used to treat Parkinson's disease can cause a similar effect. Other tyramine-containing foods to avoid if you are taking these drugs include smoked meat, aged/fermented meat, certain processed lunch meats, hot dogs, aged and mature cheeses, fermented soy products, and draft beers.

Drug Interaction Checker (not an exhaustive list)

Drug Interaction Checker (not an exhaustive list)

Always Check With Your Doctor

The information above is meant to inform only and is in no way a substitute for professional diagnosis and treatment. The table above contains information from numerous sources about generic classes of drugs and is not an exhaustive list.

In some cases, only specific subclasses of a drug present a risk for interaction. As an example, while it is generally OK to take antibiotics with milk, the tetracycline subclass of antibiotic can cause an interaction with milk. Sometimes labels advise us to take certain subclasses of antibiotic with milk to help avoid irritation of the stomach. The same class/subclass rule applies to the generic class of drug called antihistamine. Apart from terfenadine, most are OK with grapefruit juice.

Drug interactions with other drugs are also a potential source of serious side effects. These interactions are typically well known and documented, and in most pharmacies the computer software automatically checks for any potential problems.

The bottom line . . . always make certain that your doctor is aware of all medications that you are taking, including over-the-counter drugs. Doctors try to avoid prescribing medications with known food interactions, and it is usually possible for another medication to be substituted for one that is known to cause interactions.


This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.


Kenneth Avery from Hamilton, Alabama on August 13, 2014:

Hi, Kaili,

No, thank you so much for sharing this priceless information and I am following your "orders," in taking care of myself.

I have finished folding some towels and putting them away, so my work has been light today.

In the days ahead, I will send you a Personalized Thank You Note for following me. I take my followers seriously.

Kaili Bisson (author) from Canada on August 13, 2014:

Hi Kenneth, so glad I could help.

Please take good care of yourself.

Kenneth Avery from Hamilton, Alabama on August 12, 2014:

Hi, Kaili,

You are very welcome. I enjoyed this very-helpful piece.

I take a lot of medications--have been taking them since 2003 when I was diagnosed with fibromyalgia and neurothopy.

I found this hub interesting as I have to watch what I drink with my med's.

I do not mean alcohol. I do not drink, smoke, dip or chew. Or take illegal substances. Still, I have to be really careful--and like you said, various foods too.

I no longer eat pork for this past St. Patrick's Day, I stayed in bed most all day with a fever and upset stomach and come to find out, the pork and the enzymes, interacted with one of my painkillers and since then, I gave it up.

Thank you for sharing this valuable information.

And I also thank you for your following.

I Cherish all of my followers and that includes you too.

Keep up the great work.

Kenneth, one life you touched in Alabama.

Kaili Bisson (author) from Canada on August 12, 2014:

Hi Kenneth, and thank you so much for your wonderful feedback!

I was amazed that there were so many things that we take for granted relative to food and drug combinations - OTC and prescription drugs both. Scary.

Kenneth Avery from Hamilton, Alabama on August 12, 2014:


This is an excellent piece of writing. To be totally-honest, it can easily be described as amazing.

I loved every word. Graphics were superb. This hub was helpful, informative and I found it very interesting.

Voted up and all the choices because you deserve it.

You have such a gift for writing. Keep writing no matter what.


Kenneth Avery, Hamilton, Alabama

Kaili Bisson (author) from Canada on August 11, 2014:

Hi Rebecca and thank you....glad I could help :-)

Kaili Bisson (author) from Canada on August 11, 2014:

Hi Jackie and thank you. I too knew about grapefruit but was surprised by some of the others. I was fortunate too when putting this hub together that Docmo reviewed it and helped me make it better. Too many folks gulp down pills with grapefruit juice without knowing it could be a problem.

Rebecca Mealey from Northeastern Georgia, USA on August 11, 2014:

This is very informative and helpful! I am going to print out your chart for the fridge. Yay! Thanks!

Jackie Lynnley from the beautiful south on August 11, 2014:

This is such an important article! I knew about the grapefruit juice but not the other things you mention. There really is not enough warning (if any) of these foods with medicine. It is really hard to imagne how many people have grapefruit right along with their medicines every morning; or very many. I am surprised doctors do not talk about this with patients as soon as they put them on these medicines.

Kaili Bisson (author) from Canada on August 20, 2012:

Hello amanthkr01 you are welcome...and thank you for the vote and for sharing!

Kaili Bisson (author) from Canada on August 20, 2012:

Hello jainismus, you are welcome. Glad you found this information useful.

Aman Thakur from India on August 20, 2012:

This is really an awesome hub. You have very clearly defined the almost every food interaction with the common medications. Thanks for sharing this useful hub.

Voted up and shared.

Mahaveer Sanglikar from Pune, India on August 20, 2012:

hanks Kaili for writing such a useful Hub.

Kaili Bisson (author) from Canada on May 23, 2012:

Hi Marcy...thank you so much for your feedback and for sharing; much appreciated. It is really something that people need to be aware of. I believe the stat I read said 20-22% of Americans drink grapefruit juice for breakfast, and many take their meds at the same time.

Marcy Goodfleisch from Planet Earth on May 22, 2012:

FYI - I also shared this on FB - everyone should read this hub - such important information!

Marcy Goodfleisch from Planet Earth on May 22, 2012:

This is an outstanding and very thorough hub! I knew several of these, but you mentioned some that I'd not heard of. Grapefruit juice, by the way, is very often prohibited for people who are volunteering for drug research studies. In some cases, it is warned against for those on certain meds - for exactly the reasons you mention.

Thanks for this excellent hub! Voted up and up!

Kaili Bisson (author) from Canada on May 17, 2012:

Hi rajan. Thank you for the feedback and glad you found the info useful. For the chart I just used Excel and then copied it into Paint to create .jpg

Rajan Singh Jolly from From Mumbai, presently in Jalandhar, INDIA. on May 16, 2012:

This is a very useful write up on the food- drug interactions. I love the chart which you have provided.

Thanks for sharing this info, Kaili.

Voted up and all across the board.

Kaili Bisson (author) from Canada on May 16, 2012:

Hi xstatic...thank you for the feedback! I am really enjoying HubPages and I look forward to reading your hubs as well.

Jim Higgins from Eugene, Oregon on May 16, 2012:

Great information and cautionary advice. Well written too! Welcome to HubPages!

Kaili Bisson (author) from Canada on May 11, 2012:

Hi all and thank you for your feedback. I have updated the chart somewhat to note specific subclasses of antibiotic and antihistamine that can cause a problem, and have also added some text to the bottom capsule. :-)

Danette Watt from Illinois on May 10, 2012:

who would have thought that chocolate could be a bad thing? You've provided some very important information here Kaili. Great job - voted up, useful and interesting

Nell Rose from England on May 10, 2012:

This is great for me, as I have Asthma and a thyroid problem. I often wondered if I could take certain foods with my medication, so this is great. Thanks, nell

Kaili Bisson (author) from Canada on May 10, 2012:

Hi Simone and Docmo,

Thank you both for the feedback. As I posted earlier, I was trying to be as "unspecific" as possible in the text by saying "certain antibiotics" as an example, then I ended up not using the same approach in the table. I am going to make some modifications to the table especially and re-post. Tetracycline is a problem with milk, and macrobid is a problem with magnesium supplements, but in some cases we are advised to take milk to help sooth the effects of the antibiotics on the stomach lining...thanks for straightening this all out :-)

Kaili Bisson (author) from Canada on May 10, 2012:

Hi Susan and thank you for the great feedback. Yup, pretty scary that juice. And so many folks take their meds with juice at breakfast. It probably accounts for a good number of reactions to drugs and probably isn't even considered as being the culprit.

Mohan Kumar from UK on May 10, 2012:

This is a really useful hub, Kaili. It contains some very useful information for those on prescription medication. You are right about how people should be wary of interactions with common food and beverage items. The chart is a great way to capture those common interactions. Well done!

There are a couple of misleading information- not all antibiotics interact with milk and dairy mainly only tetracyclines. Penicillins are safe to take with milk. I realise you have used generic titles ( antihistamines, antibiotics) this could cause confusion as each class of drugs have many subclasses and mostly the interactions are only with a specific small subclass. Like there is only one type of antihistamine that interacts with grapefruit juice (terfenadine) all others are pretty safe ! Hope this doesn't cause some mass panic among those who are taking other standard antihistamines.

well done in raising awareness.

Susan Zutautas from Ontario, Canada on May 10, 2012:

I drink grapefruit juice almost every day. Had no idea that it may interfere with medications. Good to know.

Very useful and informative hub. Voting up, sharing and pinning for future reference.

Simone Haruko Smith from San Francisco on May 10, 2012:

Oh drat! I wish I had read this Hub before going on antibiotics for something! I had NO IDEA I should be avoiding dairy!

Thanks for the super useful Hub. LOVE the table! What a great reference point!

Kaili Bisson (author) from Canada on May 10, 2012:

Hi everyone,

Thank you all for the great feedback. I was totally shocked at all of the potential interactions out there. Drug-drug I was not surprised by, but food-drug interactions are far more common than I would have guessed. I tried to keep things pretty general, and not name "brands" but I will probably go back at this and edit to make a few more points. Grapefruit alone could have its own Hub!

Denise Handlon from North Carolina on May 10, 2012:

Great info here and wonderful topic! Well done. Thanks for sharing-rated up /U/I

kelleyward on May 09, 2012:

Excellent hub with important information! I really like the chart! As an RN I think information like this is very important! Voted up! Take care, Kelley

Arlene V. Poma on May 09, 2012:

Great topic and writing! You always need to be careful. I would be tempted to test different herbs for what they are said to offer, but there's a risk in those when it comes to combining them with prescription medication. I read somewhere that worldwide, herb manufacturers don't have to follow strict guidelines in order to market their products.

Marlene Bertrand from USA on May 09, 2012:

Wow! That chart is amazing. I have to bookmark this hub to use as a reference. Who would have thought that bananas could be potentially harmful? It just goes to show that we need to read every label of every medication we take.

DigbyAdams on May 09, 2012:

I agree that it's important to know what to eat and not eat. I was on cipro for about a month and could not eat substanial amounts of milk or yogurt, two hours before or six hours after a dose. The dose was every 12 hours. However the doctor wanted me to eat yogurt to keep the good bacteria going in my stomach and intestines. My pharmacist actually helped me decide the best time during the day (and night) to eat my yogurt.